To measure the pH of everyday substances, Year 9 students can use different methods. These methods show why pH is important in chemistry.

What is pH?

Understanding pH helps us know how substances interact and react with each other. The pH scale goes from 0 to 14.

• If a substance has a pH less than 7, it's called an acid.
• If it has a pH of 7, it is neutral.
• If the pH is greater than 7, it's called a base.

Ways to Measure pH

1. Universal Indicator Solution

   • This is a special mix of dyes that change color depending on how acidic or basic a solution is.
   • Each color tells you something about the pH level. Here’s a quick guide:
     • pH 1 (Strong Acid) - Red
     • pH 3 (Weak Acid) - Orange
     • pH 7 (Neutral) - Green
     • pH 11 (Weak Base) - Light Blue
     • pH 14 (Strong Base) - Dark Blue

2. pH Strips

   • These strips have special dyes on them and are an easy way to find the pH number.
   • You dip the strip in the solution and then compare the color to a scale on the package.

3. pH Meters

   • This is an electronic tool that gives you an exact pH number.
   • The pH meter usually has a glass part that reacts to hydrogen ions. This makes it very accurate.

Why pH Measurements Matter

• Effect on Living Things: The pH of the environment is vital for living organisms. For example, freshwater fish need a pH between 6.5 and 8.5 to survive. If the pH gets too high or too low, it can harm fish and upset local ecosystems.

• Importance in Farming: Soil pH affects how well plants grow and how nutrients are available. The best soil pH for most crops is between 6 and 7.5. If the pH is lower than this, plants can have trouble taking in nutrients, leading to less healthy crops.

• Use in Industries: Many chemical processes depend on pH. For example, making some fertilizers requires very specific pH levels.

Common Substances to Test

Students can check the pH of many common items found at home. Here are a few examples:

• Lemon juice (about pH 2): It shows citric acid is present.
• Vinegar (about pH 3): It has acetic acid.
• Coffee (about pH 5): This is mildly acidic.
• Baking soda solution (about pH 9): This is mildly basic.
• Ammonia cleaner (about pH 11): This is strongly basic.

Conclusion

By checking the pH of these everyday substances, Year 9 students can get hands-on experience with basic chemical analysis. This activity not only helps them learn about pH in theory but also shows how important pH is in daily life and in science.